Research Bonus for folderd vehicles

How comes that a folderd vehicle like the Char 25t does not give me any research bonus for the AMX-30 while the Lorraine 40t does?

For Aircraft it often is even more baffling. playing the Canberra with offensive armament doesnt give you any Bonsu for the Thunderchief, the Canberra without any offensive armament however does.

Shouldnt (ideally) both planes give me a bonus on researching the one next in line, or at least that i can choose which one will provide a bonus?